The present invention relates to a roof for a railcar, and more particularly to a composite fiberglass roof for use on standard, high cube, refrigerated and cryogenic railcars.
Today, the four most common types of railcars being used commercially for the transportation of cargo are standard, high cube, refrigerated and cryogenic railcars. A standard railcar, which is approximately 51 feet long, has a storage compartment that is approximately 9 feet high and 9 feet wide, with a storage area of over 4,000 ft3. High cube railcars are similar in construction, except they are approximately 17 feet longer and 4xc2xd feet higher than standard railcars. This added size provides a storage area of over 8,200 ft3, but also includes a height that requires a shallow roof that only extends above the railcar by a few inches. The exteriors of refrigerated and cryogenic railcars closely resemble standard or high cube railcars, but their interiors are insulated. A refrigerated railcar also contains a mechanical refrigeration system, while a cryogenic railcar includes a false ceiling above which a load of cryogenic material is stored to provide the necessary cooling of the railcar and its cargo.
Each of these railcars has a roof, which is formed of galvanized steel and includes numerous individual panels that extend transverse to the railcar and are riveted, welded or otherwise bolted to each other and to the railcar""s sidewalls. Steel roofs have been the industry standard for years, yet they have many disadvantages, as discussed below.
Conventional steel roofs are difficult to install on a railcar. Typically, the roof is formed from numerous individual panels that each have a 3 foot length and a width that is sized to span the distance between the railcar""s sidewalls. Furthermore, each panel has an upwardly extending flange extending along both of the panel""s lateral edges. Two panels are joined by placing their lateral edges next to each other and welding or riveting the flanges together. The joined flanges form a rib-like support between the panels, which must be subsequently sealed to prevent it from leaking. The roof is formed by repeating this process until enough panels have been interconnected to cover the upper surface of a railcar. This entire structure is next placed on top of a railcar, where it is welded to the railcar. The seam formed between the roof and the railcar must also be sealed. Furthermore, because the installation process can loosen or damage the seals between the individual panels, the roof must be tested to ensure it does not leak after it is installed on the railcar. Typically, the entire installation process is time-consuming and tedious, taking at least 20 man-hours to complete.
The disadvantages of using a conventional steel roof do not end once the roof is installed. An additional problem with steel roofs is that steel is expensive and extremely heavy. A conventional steel roof typically weighs more than 2,000 pounds. When mounted on a railcar, this weight raises the center of gravity of the railcar by approximately 4 or 5 inches. As a result, the railcar is less balanced and more prone to tipping. This added weight also increases the power and fuel necessary to transport the railcar, as well as the time necessary to stop the railcar.
Additional problems with steel roofs arise during their use on a railcar. As discussed, the steel roof panels typically are joined to each other and the railcar through a combination of rivets, bolts and welds, which must be sealed to prevent leakage. Even if the roof is completely sealed when first installed, the extreme vibration and torsion that the railcar and roof undergo during normal use can cause these seals, bolts and/or rivets to loosen and leak. When this occurs, water and other materials can pass through the roof, thereby exposing the railcar""s cargo to possible contamination and damage.
A further disadvantage can occur when cargo is loaded into or removed from a railcar with a steel roof. During this process, the railcar""s roof can be struck by cargo being loaded or removed, or struck by the mast of a forklift, which is commonly used to load and unload the railcar. Impact from this contact can deform the roof upward. Because the steel roof is inelastic, it does not return to its original position after the impact, but remains permanently deformed. In addition, when the roof is pushed or deformed upward, it may cause the sides of the railcar to collapse inward, thereby distorting the entire railcar. The entire railcar must then be removed from service for repair. Furthermore, contact to the roof of the railcar can also cause the roof to tear or puncture. A tear or puncture is difficult to patch because the roof is formed of galvanized steel. Therefore it is often necessary to remove and replace any punctured or torn roof panels.
Still another problem with conventional steel roofs is that they readily absorb heat from outside the railcar and do not allow light to enter the railcar. When the railcar is used on warm days, the steel construction of the roof quickly heats up and conducts this heat to the railcar""s interior. On hot days, it is possible for the interior of a railcar to reach temperatures in excess of 100xc2x0 F. Furthermore, because no light passes through the roof, external light sources must be brought into the railcar whenever it is to be loaded or unloaded. Installing external light sources not only increases the time to load or unload the railcar, but also increases the number of obstacles that must be avoided by workers when loading or unloading the railcar.
When a conventional steel roof is mounted on a refrigerated or cryogenic railcar, an insulating layer must be added beneath an existing steel roof. Installing this layer requires retrofitting a liner beneath the railcar""s steel roof.
Next, the entire roof assembly must be rigidly braced from beneath the newly installed liner. Finally, holes are drilled through the liner, and insulating material is injected though these holes. Unless the bracing and liner are very thoroughly and carefully installed, the pressure exerted by the injected insulating material is likely to cause the entire subassembly to collapse inward, thereby requiring the railcar to be cleaned and the installation process to be repeated.
In addition to this installation process, cryogenic railcars further require a false ceiling and a cryogenic supply system to be installed beneath this insulating layer. Conventional supply systems are mounted to the steel roof above the false ceiling. The ceiling typically includes individual sections that extend across the width of the railcar and are placed end-to-end beneath the supply system. If it is necessary to repair or otherwise maintain the supply system, these sections must each be removed to gain access to the supply system.
The fiberglass roof of a preferred embodiment of the invention features a composite fiberglass surface, which has a central portion and a peripheral region extending beyond the central portion. The central portion has a cross-sectional configuration that defines a first arc along the length of its cross-section. The roof also includes a plurality of spaced-apart, broad fiberglass ribs that are integrally formed in the central portion and extend both transverse to the longitudinal axis of the fiberglass surface as well as above the central portion. The ribs define a second arc that intersects the first arc. This unique, dual-arc structure, which includes broad elongate ribs, provides a fiberglass roof that is lightweight and simple, yet extremely durable and resilient. Preferably, the ribs form a unitary, seamless expanse with the fiberglass surface, and the entire roof is molded from a single sheet of composite fiberglass material.
In another embodiment of the invention, the fiberglass surface has a central portion with a lower face and a peripheral region extending beyond the central region. In this embodiment, a plurality of spaced-apart ribs are mounted on the lower face of the central portion and extend transverse to the longitudinal axis of the fiberglass surface. The ribs preferably have arcuate cross-sections, providing a fiberglass roof especially adapted for use on high cube railcars, whose height requires a roof that only extends above the railcar""s sidewalls by a few inches.
Yet another embodiment of the invention is a fiberglass roof for use on cryogenic railcars. The roof includes a bunker that defines a recess for supporting cryogenic snow. A composite fiberglass surface is mounted on the bunker to enclose the recess, and an insulating layer is disposed between the bunker and the fiberglass surface. The roof further includes a manifold for delivering cryogenic material to the bunker. The manifold has a supply tube disposed below the lower surface of the bunker and a plurality of nozzles that extend from the supply tube through the bunker""s lower surface and into the recess for forming cryogenic snow from the cryogenic material and for distributing the cryogenic snow within the recess.
These and other advantages are obtained by the invention, which is described below in conjunction with the accompanying drawings, in which embodiments are disclosed that may satisfy one or more of the above problems of conventional roofs.